1. Field of The Invention
The present invention generally relates to a servo information detection method and a disk apparatus using the same, and more particularly relates to a servo information detection method which detects servo information recorded at given intervals in a disk, as well as a disk apparatus using the servo information detection method.
2. Description of the Related Art
A description will be given of a magnetic disk drive with reference to FIG. 1A, FIG. 1B and FIG. 2.
As shown in FIG. 1A and FIG. 1B, the magnetic disk drive 100 generally includes a disk enclosure (DE) 110 and a printed circuit board (PCB) 120. The magnetic disk drive 100 is, for example, a hard disk drive (HDD).
In the disk enclosure 110, a magnetic disk 111, a spindle motor (SPM) 112, an arm 114, and a voice coil motor (VCM) 115 are provided. In a case of the hard disk drive (HDD), a plurality of magnetic disks are rotated by a spindle motor at the same time. However, in the following description, such magnetic disks are collectively referred to as the magnetic disk 111, for the sake of convenience of description.
In the magnetic disk drive 100, the printed circuit board 120 supplies a drive signal to the spindle motor 112 so that the spindle motor 112 is driven to rotate the magnetic disk 111 around the central axis of the spindle motor at a constant velocity in a rotation direction indicated by the arrow A in FIG. 1B. The printed circuit board 120 supplies a drive signal to the voice coil motor 115 so that the voice coil motor 115 is driven to swing or rotate the arm 114 around the central axis of the voice coil motor in a rotation direction indicated by the arrow B in FIG. 1B. The magnetic head 113 is attached to the leading edge of the arm 114. By the swinging movement of the arm 114 in the direction B, the magnetic head 113 at the leading edge of the arm 114 is moved in a radial direction of the magnetic disk 111.
As shown in FIG. 2, the disk enclosure (DE) 110 further includes a head controller (Head IC) 116. During a read operation, the head 113 electromagnetically generates a readout signal from the disk 111 and supplies the readout signal to the head controller 116. The head controller 116 amplifies the readout signal received from the head 113. The amplified readout signal from the head controller 116 is supplied to the printed circuit board 120. During a write operation, the head controller 116 amplifies a writing signal that is to be recorded in the disk 111, and supplies the amplified writing signal to the magnetic head 113.
As shown in FIG. 2, in the printed circuit board (PCB) 120, a hard disk controller (HDC) 121, a random access memory (RAM) 122, a flash read-only memory (Flash ROM) 123, a microprocessor unit (MPU) 124, a read channel (RDC) 125, a servo controller (SVC) 126, and linear acceleration sensors 127 and 128 are provided.
As described above, the head 113 generates a readout signal from the disk 111, and the readout signal from the head 113 is amplified by the head controller 116. The amplified readout signal, output by the head controller 116, is supplied to the hard disk controller (HDC) 121 through the read channel 125 in the printed circuit board (PCB) 120. The amplified readout signal is subjected to a decoding process at the HDC 121. The HDC 121 supplies the readout information, which is produced through the decoding process from the amplified readout signal, to an external host system 130.
Further, writing information is supplied from the host system 130 to the HDC 121. The writing information is subjected to an encoding process at the HDC 121. The HDC 121 supplies the encoded signal, which is produced through the encoding process from the writing information, to the head controller 116 of the disk enclosure (DE) 110 via the read channel 125. The encoded signal is amplified by the head controller 116. The head controller 116 supplies the amplified signal to the head 113, so that the writing information is electromagnetically recorded in the disk 111 by using the head 113.
FIG. 3A and FIG. 3B show a format of servo information of the magnetic disk 111 that is used by the magnetic disk drive.
As shown in FIG. 3A, a sequence of servo information blocks SB0, SB1, . . . , SBn is recorded at given intervals xe2x80x9ct0xe2x80x9d in the magnetic disk 111. Normally, by using a servo track writer STW (not shown), the servo information blocks SB0, SB1, . . . , SBn are recorded, in advance, in the respective sectors of the magnetic disk 111.
As shown in FIG. 3B, each of the servo information blocks SB0, SB1, . . . , SBn is comprised of servo sync mark SM, cylinder number CYL, and position information POS. Generally, when all of the servo sync marks SM are detected from the disk 111, it is determined as detecting the sequence of servo information blocks SB0, SB1, . . . , SBn.
In a conventional disk apparatus, when the entire bit pattern of the servo sync marks SM, detected by the conventional disk apparatus from the magnetic disk 111, matches with a given comparison bit pattern, the presence of the servo sync mark SM in the detection bit pattern is detected. However, if a medium defect with respect to at least one bit among the bit pattern of the servo sync marks exists in the disk, the match does not occur and the absence of the servo sync mark in the detection bit pattern is detected. In the latter case, the conventional disk apparatus generates indication of an error that indicates which sector of the disk is a defective sector including the defect. That is, the conventional disk apparatus cannot correctly detect the presence of the servo sync mark in the detection bit pattern if the detection bit pattern contains a bit affected by an insignificant defect on the disk.
An object of the present invention is to provide an improved servo information detection method that accurately and reliably detects the servo information in the disk without being influenced by an insignificant defect on the disk.
Another object of the present invention is to provide a disk apparatus using an improved servo information detection method that accurately and reliably detects the servo information in the disk without being influenced by an insignificant defect on the disk.
The above-mentioned objects of the present invention are achieved by a servo information detection method for detecting a servo sync mark of a disk, the method comprising the steps of: determining whether a pattern of detection bits, detected from a vicinity of the servo sync mark of the disk, matches with a given comparison bit pattern; and changing a pattern of tolerance bits based on a location of the disk where the servo sync mark is detected, so that the matching between the detection bit pattern and the comparison bit pattern is performed based on the changed tolerance bit pattern.
The above-mentioned objects of the present invention are achieved by a disk apparatus in which a servo sync mark of a disk is detected, the disk apparatus comprising: a determination unit which determines whether a pattern of detection bits, detected from the servo sync mark of the disk, matches with a given comparison bit pattern; and a control unit which changes a pattern of tolerance bits based on a location of the disk where the servo sync mark is detected, so that the determination unit is allowed to perform the matching between the detection bit pattern and the comparison bit pattern based on the changed tolerance bit pattern.
The servo information detection method and the disk apparatus of one preferred embodiment of the present invention are effective in accurately and reliably detecting the servo information in the disk without being influenced by an insignificant defect on the disk. Even if a medium defect of the size of 1 bit or more is included in the detection bit pattern, the presence of the servo sync mark therein can be reliably detected without causing an error. It is possible to prevent the reduction of the amount of storage available to the disk due to the defective sector or the like.